A new study follows an analysis earlier this year revealing that the symptoms comprise a new sea lion disease.

Domoic acid concentrations rise at times due to natural, climactic factors, the authors point out. But other human-made chemicals may be making the sea lions more susceptible.

"This is probably just the beginning to understand how not just a single chemical, but a complex mix of chemicals we start life with can leave us vulnerable to disease later in life," said study co-author John Ramsdell, a physiologist with the National Oceanic and Atmospheric Administration (NOAA).

He believes the new study, published in the current issue of the online journal Marine Drugs, also has implications for human health.

Poisoned Before Birth

Toxin-producing algal blooms are natural, cyclical events.

"What's fascinating about this work is how the natural rhythms of boom and bust in the sea can conspire to send a pulse of toxin through the food web " said Christopher Scholin, a scientist with the Monterey Bay Aquarium Research Institute, who was not involved with the study.

"If the timing is right, the effects of that pulse long outlive the immediate impacts of the bloom," he said, adding that "chronic exposure to [the toxin] clearly has lasting impacts on marine life."

Domoic acid has previously been blamed for die-offs of seabirds such as pelicans and cormorants.

Ramsdell, the study co-author, said sea otters, whales, and dolphins are also commonly poisoned by domoic acidnot only in California, but in nearly all coastal waters in the United States. More rarely, domoic acid has sickened and killed humans.